Global Religious Demographics: A Decade of Change
Between 2010 and 2020, significant shifts reshaped the world's religious map. While most major faiths expanded in number alongside population growth, Christianity's share of the global population notably declined. Meanwhile, Islam emerged as the fastest-growing religion, and Hinduism maintained a steady presence. The population of those unaffiliated with any religion also rose considerably, largely driven by former Christians leaving the faith.
Christianity’s Declining Share Despite Growth
Globally, Christians remain the largest religious group, increasing from 2.18 billion to 2.30 billion over the decade, adding roughly 122 million adherents. However, their proportion of the global population dropped from about 30.6% to 28.8%. This decline isn’t due to shrinking birth rates but largely attributed to religious disaffiliation and switching away from Christianity.
Among young adults worldwide, for every individual converting to Christianity, three raised as Christians leave the faith. This dynamic offsets their demographic advantage provided by comparatively higher fertility rates.
Islam’s Remarkable Rise Fueled by Demographics
Islam saw the fastest increase, gaining an estimated 347 million new adherents to reach around 2 billion. Its global share rose by 1.8 percentage points to 25.6%. This growth stems primarily from demographic factors: Muslims are generally younger (average age 24 versus 33 for non-Muslims) and have higher fertility rates, leading to more natural population growth.
Stability and Decline Among Other Faiths
- Hinduism grew to about 1.2 billion, maintaining a steady global share near 14.9%.
- Judaism saw a modest gain, rising from roughly 13.8 million to 14.8 million adherents, representing about 0.2% of the world population.
- Buddhism was the sole major religion to shrink in absolute numbers, declining from 343 million to 324 million due to low fertility and losses through religious switching.
- The category of “other religions” (including Baha’is, Jains, and various folk traditions) grew in line with general population trends, holding at roughly 2.2% worldwide.
The Rise of the Religiously Unaffiliated
The religiously unaffiliated now make up 24.2% of the global population, up from 23.3% in 2010. This increase largely comes from people raised Christian who have chosen to disaffiliate. Despite demographic disadvantages like older average age and lower birth rates, the unaffiliated have grown due to cultural shifts and widespread secularization in many regions.
Regional Trends: Where Religion is Thriving or Waning
Sub-Saharan Africa: A Hub for Christianity
Sub-Saharan Africa has emerged as a significant center for Christianity, now accounting for about 31% of the world’s Christians, up from 24.8% a decade ago. High fertility rates and a youthful population underpin this expansion, even as Christianity’s share declines in Europe. Countries like Mozambique saw notable increases in Christian populations.
Unaffiliated Majority in Key Nations
The religiously unaffiliated dominate in several populous countries. In China, about 1.3 billion people are unaffiliated, despite many maintaining personal beliefs sans official religious identity. Large numbers also reside in the United States (101 million) and Japan (73 million), reflecting growing secular trends.
Factors Driving Religious Shifts: Demography and Switching
Demographic Drivers
- Age Structure: Younger populations increase growth potential through more individuals in childbearing years.
- Fertility Rates: Higher birth rates translate into faster population growth within religious groups.
- Mortality Rates: Though less influential, they also affect group sizes.
- Muslims benefit from both youthful demographics and higher fertility, while groups like Buddhists face demographic challenges.
Religious Switching
Shifts in religious identity—whether through conversion or disaffiliation—have profoundly influenced growth patterns. Christian losses through disaffiliation contrast with gains among the unaffiliated, who primarily attract former Christians. Hindu and Jewish populations see minimal switching, contributing to their steady numbers. Buddhists’ decline is partially due to people moving away from the religion.
What Lies Ahead? Anticipating Future Trends
- Christianity remains the largest religion but faces ongoing challenges as its global share declines.
- Islam’s growth trajectory suggests it may approach parity with Christianity by mid-century.
- The unaffiliated segment is likely to continue expanding in many regions, driven by cultural shifts.
These evolving religious landscapes carry broad implications. Secularization trends, especially in developed countries, may reshape societal norms and policies. Meanwhile, in regions like sub-Saharan Africa and parts of Asia, religious identity will likely remain a central element of culture and governance.
